1. Field of the Invention
The present invention relates to a conditioner for polishing pad and a method for manufacturing the same, and more particularly to a conditioner for polishing pad to be used in chemical mechanical polishing (CMP) process and a method for manufacturing the same.
2. Description of the Prior Art
Generally, chemical mechanical polishing is widely used in the manufacturing process of semiconductor devices to obtain smooth and even surfaced wafers. Typically, a wafer to be polished is held by a carrier positioned on a polishing pad attached above a rotating platen (not shown), then by applying slurry to the pad and pressure to the carrier, the wafer is polished by relative movements of the platen and the carrier. A conventional polishing pad used for chemical mechanical polishing process generally comprises a multitude of fine holes having a diameter size of 30-70 m for exhibiting pumping effect when pressure is applied to the polishing pad to achieve a high removal rate. However, after a prolonged use, the holes wear out and become deposited with polishing residues, causing an uneven surface of the polishing pad. As a result, its ability to polish wafers decreases in time and the effectiveness of CMP process of achieving an uniformly even wafer surface becomes diminished.
To recover the polishing performance and to compensate for the uneven surface of the polishing pads, conditioning process utilizing a conditioner for removing the uneven surface of the polishing pads is commonly implemented by CMP process.
FIGS. 1A to 1C show a structure of a diamond conditioner used for conditioning polishing pads, which is manufactured by conventional electro-deposition method. Such diamond conditioner is typically made from an electro-plated diamond disk in which diamond particles 16 are scattered onto a stainless steel body portion 10 and electro-deposited by bonding metal 18 such as nickel or made from a brazed diamond disk in which diamond particles 16 are fixed onto the body portion 10 by melting the bonding metal 18.
However, the conditioners made from such electro-deposition and braze methods have cutting surfaces of an uneven height caused by irregular distribution and varying sizes of the diamond particles 16 as illustrated by a cutting portion 12 in FIG. 1C. Particularly, having diamond particles with diameter size beyond the range of 150-250 m in the conditioner cutting surface causes an undesirable surface roughness.
Further, because the conditioners having the above structure polishes wafers by making partial point contact and due to obtuse cutting angles of diamond particles, the cutting efficiency obtained by such conditioners is low. As such, in order to improve the cutting efficiency, it is necessary to apply high pressure in the conventional conditioning processes. In conventional polishing pads having a dual-pad structure commonly made from polyurethane material, CMP is carried out in top pad while bottom pad provides pressure required for the conditioning process. When high pressure is applied to the top pad by conditioner during the conditioning process, due to the compressibility of the bottom pad, the conditioning cannot be smoothly carried out. Thus, maintaining a flat and leveled polishing pad surface becomes a difficult task.
More, the conditioners made from electro-deposition and brazed methods does not provide grooves or ditches for draining particles from the polishing pads. As a result, residual particles deposit and accumulate on the conditioner surface, which further attributes to decreasing the conditioning effectiveness.
Conventionally, the conditioning process can be carried out simultaneously with CMP process. Such in-situ conditioning process are classified into oxide or metal CMP processes by the type of slurry used for the polishing process, which is typically constituted by silica, alumina or ceria polishing materials. The slurry used for oxide CMP generally has a pH value within 10-12, while the slurry used for metal CMP has a pH value less than 4, and the bonding metal 18 used for fixing the diamond particles 16 onto the cutting surface of the conditioner is nickel, chromium or the like metals. In implementing either oxide or metal CMP in-situ conditioning process, because the polishing process is simultaneously carried out with conditioning process, the bonding metal 18 holding the diamond particles 16 is also affected by slurry, resulting in frequent detachments of the diamond particles 16 from the conditioner surface. Further, in metal CMP in-situ conditioning process, the strong acid property of the slurry used for the process has a tendency to corrode the bonding metal 18 to weaken its bonding effect, which ultimately causes the detachments of the diamond particles 16.
The detached diamond particles 16 usually attach to the surface of the polishing pads and impart fatal scratches to the wafer surface during the polishing process to cause high defective rates in the semiconductor manufacturing process. Consequently, the polishing pads must be frequently replaced.
Further, metal ions from the eroded bonding metal 18 in metal CMP in-situ conditioning process often attaches to metal lines of the wafer circuits to cause short-circuits. In addition, metal ions from the in-situ conditioning process substantially attributes to the metal ion contamination of the wafers, and because the resulting semiconductor defects caused by the contamination are detected at the later manufacturing stages, its impact in the loss incurred from the defects is considerable in the industry.
In view of the foregoing, it is an object of the present invention to provide a conditioner for polishing pad which has an excellent and uniform degree of surface roughness for preventing defects caused from the detachments of diamond particles and metal ion contamination and for effectively conditioning the polishing pads in absence of high pressure in chemical mechanical polishing process for the semiconductor wafers.
It is a second object of the present invention to provide a method for manufacturing a conditioner for polishing pad which has the characteristics and functions of the above described conditioner.
According to the present invention, there is provided a conditioner for polishing pad comprises a substrate having integrally formed with a plurality of geometrical protrusions in an uniformed height on at least one side of the substrate and a diamond layer of an uniformed thickness formed substantially on a whole surface of the substrate side having geometrical protrusions.
It is preferred that the above geometrical protrusions have rectangular or cylindrical shapes and have flat and even upper surfaces. Optionally, the upper surfaces of the geometrical protrusions can have a plurality of smaller geometrical protrusions formed by a pair of diagonally-crossed grooves having U or V cross-sectional shapes or by a number of crossed-strips of grooves having U or V cross-sectional shapes. The smaller geometrical protrusions formed on the upper surfaces of the geometrical protrusions have a plane-view shape of triangle, rectangle or rectangular pyramid.
The plurality of geometrical protrusions integrally formed on the surface of the substrate has a crossed-strip pattern realized by crossing-strips of ditches having U or V cross-sectional shapes, where the U or V cross-sectional shapes are defined by a side portion of the geometrical protrusions and a bottom portion of the ditches. The crossing-strips of ditches all have same width and or depth, or alternatively a ditch having a greater width and or depth can be formed at an interval of a certain number of ditches on the crossed-strip pattern as a region dividing ditch.
The substrate is not limited by any shapes as long as a plurality of geometrical protrusions can be realized on its surface. For example, the substrate can have a shape of a disk, a doughnut or a plate having multiple corners, or on one side of substrate an outer ring portion can be formed raised above a middle portion to obtain a substrate having a cross-sectional profile of a cup. Alternatively, the doughnut shape substrate can have an outer belt portion having formed with a number of segmented portions separated by valleys radially expanding from a center of the substrate on which a plurality of geometrical protrusions can be formed.
The diamond layer is thinly and evenly deposited on the substrate surface by chemical vapor deposition (CVD) method.
It is preferred that the substrate is made from ceramic or cemented carbide materials.
The conditioner of the present invention further comprises a body portion formed at a side opposite to the side having formed with geometrical protrusions, which functions to link the conditioner with conditioning equipments. It is preferred that the body portion is made from stainless steel, engineering plastic or ceramic.
In another preferred aspect of the present invention, the conditioner has a segmented shape, in which the body portion has a cross-sectional shape of a doughnut with flattened upper and lower surfaces or a cross-sectional shape of a cup. The conditioner also comprises a number of independent segmented cutting portions separated by a certain distance and fixedly attached to one of surfaces of the body portion to take on a shape of a belt, where the independent segmented cutting portions are realized on their respective substrates made from ceramic or cemented carbide materials. Further, a diamond layer having an uniform thickness is substantially formed on the whole surface of the substrate.
The conditioner of the present invention having a structure of various-types of shape is manufactured by a method comprising the steps of a) forming crossed-strips of ditches on a substrate having a certain shape to form a plurality of geometrical protrusions in an uniformed height on a surface of the substrate by utilizing a strong cutting wheel such as diamond wheel, and b) forming a diamond layer of an uniformed thickness coated substantially on a whole surface of the substrate processed by step a) by chemical vapor deposition (CVD).
Prior to implementing step b), the method can optionally comprise the step of forming a certain number of grooves in predetermined crossing directions to form a plurality of smaller geometrical protrusions in an uniform height on surfaces of the geometrical protrusions by grind and or cutting processes.
The substrate to be formed with ditches can have a plurality of shapes as already described earlier and the geometrical protrusions are realized by recessed depressions of ditches formed by grind and or cutting processes. The ditches formed in a layout of crossed-strips renders the resulting geometrical protrusions to have a pattern of crossed-strips on the substrate surface.
Prior to implementing step a), it is preferred that the method further comprises the steps of subjecting the substrate to fine grinding and lapping processes to obtain an uniform surface on at least one side of the substrate and to obtain substantially parallel substrate surfaces.
Alternatively, the step of forming geometrical protrusions on the substrate surface as outlined in step a) can be implemented by molding process in which a predetermined molding composition is injected and cooled in a mold having the shape of a substrate with geometrical protrusions.
The method may further comprises the step of attaching a body portion to the substrate at a side opposite to the side having formed with geometrical protrusions for linking the conditioner to conditioning device.
It is preferred that the substrate is made from ceramic or cemented carbide materials and the body portion is made from stainless steel, engineering plastic, ceramic or the like material.